US3943437A - Apparatus for investigating the electrostatic properties of powders - Google Patents

Apparatus for investigating the electrostatic properties of powders Download PDF

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Publication number
US3943437A
US3943437A US05/542,269 US54226975A US3943437A US 3943437 A US3943437 A US 3943437A US 54226975 A US54226975 A US 54226975A US 3943437 A US3943437 A US 3943437A
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United States
Prior art keywords
fixed plate
openings
plate
probe
rotor
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US05/542,269
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English (en)
Inventor
Marcel Mourier
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Rhone Poulenc Industries SA
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Rhone Poulenc Industries SA
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/60—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrostatic variables, e.g. electrographic flaw testing
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R5/00—Instruments for converting a single current or a single voltage into a mechanical displacement
    • G01R5/28—Electrostatic instruments

Definitions

  • the present invention relates to apparatus for measuring the electrostatic properties of powder.
  • E. an electrical connection comprising a revolving contact which makes it possible to transmit to the charging electrode an electrical voltage with an absolute value of between 2 and 20 kV, and
  • F an electrical connection comprising a revolving contact which makes it possible to transmit to the measuring components the signals captured by the measuring probe.
  • an apparatus for measuring the electrostatic properties of materials comprising a first fixed plate, a rotor mounted to rotate about an axis perpendicular to the first fixed plate, openings in the first fixed plate, openings lying along the circumference of a circle, the center of said circle lying on said axis of said rotor, an electrode and a probe fixed to said rotor and spaced apart from one another and positioned whereby both the electrode and the probe separately overlie each of said openings in turn when the rotor rotates, means for charging said electrode, means for detecting the charge on said probe, and thereby detecting the charge on said materials, a second fixed plate having means to hold it against said first fixed plate, cavities in said second fixed plate at locations overlying the openings in said first fixed plate, at least one porous element at the bottom of each said cavity and means for sucking air at the bottom of the said cavities through said porous elements.
  • FIG. 1 is a view in section of the measuring head
  • FIG. 2 is a diagrammatic view of the measuring head connected to a control box
  • FIG. 3 is a view from below of the rotor of the measuring head along the section line cc of FIG. 4;
  • FIG. 4 is a view from the left of the rotor, positioned as in FIG. 1, of the measuring head;
  • FIG. 5 is a sectional perspective view of the insulating bush and the measuring probe.
  • the measuring head shown in FIG. 1, comprises a first plane fixed plate 1 of conducting material, usually metallic, carrying an earthing terminal.
  • This plate 1 is provided with equidistant openings 2 distributed over the circumference of a circle of diameter d.
  • An electric motor 3 is fixed to a support 4 connected to the plate 1 by struts 5. These struts may be extended beyond the plate 1 by insulating feet, not shown, of a height of generally less than 5 mm.
  • the shaft 6 of the motor is connected to a lead, not shown, for earthing it, and is arranged perpendicular to the plate 1 at the center of the previously defined circumference.
  • a circular rotor 7 is fixed to the shaft 6; advantageously, it is secured by the screw 8 and can therefore be rotated by the motor.
  • An electrode 9, charging by corona effect, and a measuring probe 10 are arranged in the rotor 7 opposite the plate 1, parallel to the latter and at a mean distance from the axis of the rotor equal to the mean distance of the openings 2 to the center of the circumference of a circle of diameter d.
  • a handle (not shown) may also be provided to facilitate manipulation of the measuring head.
  • the charging electrode 9 is connected to a rotating contact 14 permitting its electrical connection to a high-tension D.C. generator.
  • the rotating contact may be a carbon wiper 14 held by a spring 15 against a conducting circular track 17, for example of metal, of means diameter D.
  • the carbon wiper 14 is connected to the electrode 9 by a sheathed wire 16. It is moved by the action of a spring 15 in the interior of a recess in insulating material 49 fixed to the rotor 7.
  • the track 17 is fixed to the plate 1 by means of an insulating support of the same diameter.
  • the track is connected by a flexible cable 19 permitting its electrical connection to a high-tension generator, the whole being constructed to permit raising the charging electrode to a positive or negative potential of between 2 and 20 kV.
  • the measuring probe 10 consists (see FIG. 5) of a metal plate of area substantially equal to that of the openings 2. It is extended by an axial shank 23 and is insulated from earth by a supporting sleeve 20, for example of polytetrafluorethylene.
  • the shank of the probe is provided with a passage 24 and the sleeve is cylindrical and is provided with two passages, one 21 axial, the other 22 radial.
  • the shank 23 is forcibly inserted in the passage 21 until the passages 22 and 24 are in line with each other.
  • the sleeve 20 is fitted in the recess 25 of the rotor (see FIG. 3).
  • the probe 10 fixed to the rotor 7 is connected electrically to a rotating contact permitting its connection to the measuring elements.
  • the rotating contact and its electrical connection are composed as follows:
  • the contact is formed of a ball bearing 32.
  • the outer race of the bearing is connected to the probe 10 by a sheathed wire 26 housed in a passage 27 of the rotor 7, and in the passage 22 extending the passage 27. This race is held inside an insulating piece 30 secured to the rotor 7 inside a cylindrical recess 31.
  • the inner race of the bearing is fitted around a fixed rod 28 held on the plate 1 by the insulating strut 29.
  • the rod 28 is connected to the measuring elements first by a sheathed wire 33 housed in a groove of the plate 1 as far as a strut 5, then from there to an armoured cable 34 to the control box shown in FIG. 2. (For greater clarity, the wire 33 has been shown in FIGS. 1 and 2 as being outside the plate 1.).
  • the openings 2 of the plate are preferably so distributed that the shortest distance between two consecutive openings is substantially equal to the width of an opening.
  • Each opening has generally a symmetrical form relative to a radial plane (for providing a symmetrical signal); the dimensions of these openings and their interspacing are predetermined for providing a substantially sinusoidal measuring signal.
  • the probe has preferably the same shape as the openings.
  • the openings and probes are circular and of the same diameter.
  • the measuring head according to the invention may, for its use, be connected to any high-tension D.C. generator, the polarity of which may be selected and which may be capable of supplying a tension between 2 and 20 kV.
  • the charging electrode is supplied with a tension of between 3 and 10 kV.
  • the measuring probe may be connected to any conventional apparatus capable of measuring electrical charges.
  • FIG. 2 shows the measuring head connected to a control box accommodating the high-tension generator and the measuring elements.
  • a control box of this type permits full use to be made of the possibilities afforded by the measuring head.
  • the charging electrode 9 is supplied by a conventional electrostatic generator 35 capable of supplying a continuous, effective high tension, the polarity of which may be selected by means of the high tension relays 36 and 37 and switch 38, connected by the connecting cable 19 to the contact track 17.
  • a cable 34 leading to an insulated cable, is an amplifier 39 provided with a gain control by potentiometer 40.
  • the amplifier is connected to a circuit 41 for detecting the amplified signal and to a moving coil milliammeter 42.
  • timing circuit 43 comprising a generator 44 supplying electrical pulses at regular intervals, and one or more pulse counters, such as 45, each controlled by a relay 46, itself actuated on the passage of the milliammeter needle.
  • a timing circuit 43 comprising a generator 44 supplying electrical pulses at regular intervals, and one or more pulse counters, such as 45, each controlled by a relay 46, itself actuated on the passage of the milliammeter needle.
  • the control box may be connected to the mains or possibly it may be supplied by an independent source of voltage.
  • a second fixed plate 50 has its upper face 51 positioned opposite the first fixed plate 1 and a gasket 52 is preferably interposed between the block and the plate.
  • the plate 50 has a raised rim 53 and a lateral groove 54 corresponding to a lateral rib of the plate 1. These means make it possible to guide, center and hold the plate 1 in a fixed position relative to the plate 50.
  • a space 59 is provided inside the plate 50, and inside a part of this there can be placed two coaxial discs 55 and 56, having similar orifices 57 and 60 corresponding to the openings 2 of the plate 1. These orifices are again equidistant and distributed over a circle of diameter d.
  • a porous element 58 is placed inside each of these orifices so that there are facing the openings 2, the same number of cavities 60, which can preferably be superposed over the said openings.
  • the remainder of the space 59 extends between the plate 50 on the one hand and the discs 55 and 56 on the other hand, the space communicating with the exterior via a pipeline 61.
  • This pipeline connects the space 59 to means of any known type (not represented), such as a vacuum pump with its accessories, for sucking air through the porous elements 60.
  • the device according to the present application functions in the following way.
  • Each cavity 60 above the porous element 58 is filled with the pulverulent or granular product to be investigated.
  • the remainder of the apparatus is then placed on the plate 50 and thereafter, by means of the device for sucking air, air is sucked through the product to be investigated and the porous element.
  • the suction effect is the stronger, the lower are the density and the particle size of the pulverulent product.
  • Measurements are then made, by connecting the apparatus to a high-tension generator and to a measuring apparatus, preferably to the previously described control box.
  • the constant speed motor is started and rotates the rotor 7 and hence the charging electrode 9 and the measuring probe 10.
  • a voltage is applied to the charging electrode after the desired polarity has been selected by means of the switch 38; the sheet is charged by corona effect.
  • the measuring probe 10 When the measuring probe 10 is opposite an opening 2 allowing the charged specimens to appear, it acquires a charge by induction. This charge is substantially proportional to the potential to which the specimen is raised and to the capacitance of the probe relative to the specimen. During the rotation of the rotor 7, the area of the probe opposite the specimen varies, the capacitance of the whole varies and consequently so does the charge acquired by the probe.
  • the input circuit of the amplifier 39 to which the probe 10 is connected by the cable 34, is composed of resistances and consequently offers slight reactance; therefore the input signal received by the amplifier is proportional to the variation in time of the electric field to which the probe is subjected during its passage past the specimen opposite the openings.
  • the curve of variation of the signal is the derivative with respect to time of the charge acquired by the probe. This charge, first increasing and then decreasing, has the form of an alternation. Since the probe is periodically adjacent to two consecutive openings, two consecutive periods succeed each other without discontinuity and the variation of the potential of the probe appears in the form of an alternating periodical signal, which is easily amplified and detected. The amplitude of the signal is proportional to the potential to which the specimen is raised.
  • the charging tension is maintained for the necessary time (generally between 5 and 50 seconds) for the specimen to acquire a maximum charge; the gain control 40 of the amplifier 39 is operated to bring the needle of the milliammeter 42 to a predetermined position.
  • the charging electrode is then disconnected from tension, which triggers the operation of the pulse generator 44 for producing on the pulse counters 45 the automatic display of the times of half-discharge, three-quarter discharge and generally preselected discharge fractions.
  • the apparatus Before making measurements with the apparatus described, it may be necessary to calibrate it for verifying that it is functioning properly, for example after transport.
  • To perform this calibration it is possible for example to place under the plate 1 of the measuring head a conducting metal sheet insulated from the said plate and from earth. This plate is raised to a known potential supplied directly by the control box, the motor is started and the measuring circuit is connected up. The needle of the milliammeter 42 is then brought to a predetermined value (corresponding to the maximum of the scale) by means of the potentiometer 40 and the value indicated by the potentiometer index is read. The apparatus is in working order when the value as read corresponds to the value predetermined in the laboratory.
  • the apparatus may be used in two distinct ways for determining the characteristics of the material alone (paint) or the material of its support.
  • the plate 1 of the measuring head is placed directly on the paint.
  • highly insulating feet are placed between the plate 1 and the material.
  • the automatic discharge time display device it is possible to connect the automatic discharge time display device to an oscilloscope or to a recorder (not shown).
  • the apparatus shown in FIG. 1 may be the object of various embodiment modifications.
  • the ball bearing 32 may be replaced by a roller or needle bearing. It is also possible to use corresponding ball, roller or needle thrust bearings. Preferably, these elements are sealed, particularly against dust.
  • the transmission of the measuring signal may also be effected by means of a rotating contact formed by a flexible blade wiping a shaft.
  • the track 17 of the rotating contact supplying the charging electrode may be arranged on a diameter less than that of the recess 31. It may also be fixed either to the plate 1, support 4, or struts 5. It is also possible to change over the connections of the rotating contacts. Many other modifications will occur to the person versed in the art.
  • the function of the porous element is, on the one hand, to support and retain the pulverulent or granular product to be investigated, and on the other hand, to allow air to pass with a low pressure drop.
  • the product to be investigated is thus held statically in the cavity 60, without the relative position of the elements of which it is composed being substantially changed at the surface, despite the air movements which take place during the measurements.
  • the electrostatic behavior of the product investigated during its discharge is thus not substantially changed.
  • the device which forms the subject of the present application thus makes it possible to investigate the electrostatic behavior of pulverulent or granular products under the same conditions, and particularly with the same precision and the same reliability, as in the case of compact materials.
  • Grids, sieves, woven fabrics, non-woven fabrics and the like can be used as porous elements.
  • Conducting materials for example sintered metals, are preferably used.
  • the various parts such as the plate 50 of the discs 55 and 56 are advantageously made of conducting materials, for example metal.
  • the plate 50 generally possesses an earthing terminal (not shown).
  • the apparatus makes it possible to investigate the electrostatic behavior of pulverulent or granular materials of very diverse nature, and especially plastics, the particle size of which is most frequently between 1 and 5,000 microns and more particularly between 20 and 500 microns.
  • Apparatus as shown in the drawings is used. It has nine cavities of diameter 16 mm and depth 3 mm, distributed over a circle of diameter 80 mm. The bottom of each cavity is lined with a sintered stainless steel disc of thickness 2 mm and porosity 10 ⁇ .
  • the disc which carries the charging electrode and the measuring probe is driven at a speed of 1,500 revolutions/minute. It moves at a distance of 2.5 mm from the samples investigated. An absolute pressure of 10 mm of mercury is maintained under the porous elements.
  • This table shows the time necessary ("Discharge time in seconds” column) for a particular sample to be discharged to the extent, expressed as a percentage, indicated in the right-hand column.
  • the first three experiments show differences in the electrostatic behavior, during discharge, of samples of various natures.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • Electrochemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
  • Electrostatic Separation (AREA)
  • Measurement Of Current Or Voltage (AREA)
US05/542,269 1974-01-21 1975-01-20 Apparatus for investigating the electrostatic properties of powders Expired - Lifetime US3943437A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR74.01915 1974-01-21
FR7401915A FR2258632B2 (enrdf_load_stackoverflow) 1974-01-21 1974-01-21

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US (1) US3943437A (enrdf_load_stackoverflow)
JP (1) JPS50127670A (enrdf_load_stackoverflow)
BE (1) BE824572A (enrdf_load_stackoverflow)
CH (1) CH592313A5 (enrdf_load_stackoverflow)
CS (1) CS182830B4 (enrdf_load_stackoverflow)
FR (1) FR2258632B2 (enrdf_load_stackoverflow)
GB (1) GB1480296A (enrdf_load_stackoverflow)
IT (1) IT1031060B (enrdf_load_stackoverflow)
NL (1) NL7500371A (enrdf_load_stackoverflow)
SE (1) SE7500576L (enrdf_load_stackoverflow)

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4885543A (en) * 1988-02-16 1989-12-05 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Electrostatic discharge test apparatus
WO1996037786A1 (en) * 1995-05-26 1996-11-28 Tr-Tech Int. Oy A measuring system and a method for detecting static electricity and/or change thereof in a measuring object and use thereof
US5604438A (en) * 1995-03-06 1997-02-18 The United States Of America As Represented By The Secretary Of The Navy Controlled spark ignition testing apparatus
US5699649A (en) * 1996-07-02 1997-12-23 Abrams; Andrew L. Metering and packaging device for dry powders
US5960609A (en) * 1998-06-12 1999-10-05 Microdose Technologies, Inc. Metering and packaging method and device for pharmaceuticals and drugs
US6428809B1 (en) 1999-08-18 2002-08-06 Microdose Technologies, Inc. Metering and packaging of controlled release medication
US20030155388A1 (en) * 2002-02-05 2003-08-21 Solystic Method of detecting plastics articles, and a detector device
US6686743B2 (en) 2000-10-24 2004-02-03 Univation Technologies, Llc Apparatus for measuring the static charge of flowable solids
US20050158366A1 (en) * 1999-04-27 2005-07-21 Richard Fotland Method and apparatus for producing uniform small portions of fine powders and articles thereof
US20070087048A1 (en) * 2001-05-31 2007-04-19 Abrams Andrew L Oral dosage combination pharmaceutical packaging
US20090087483A1 (en) * 2007-09-27 2009-04-02 Sison Raymundo A Oral dosage combination pharmaceutical packaging
US20090090361A1 (en) * 2007-10-09 2009-04-09 Anand Gumaste Inhalation device
US20110162642A1 (en) * 2010-01-05 2011-07-07 Akouka Henri M Inhalation device and method
CN103954850A (zh) * 2014-04-22 2014-07-30 重庆大学 一种运动控制机构外置的表面电荷测量系统和测量方法
CN104991129A (zh) * 2015-03-27 2015-10-21 华北电力大学 一种真空绝缘子表面电荷三维测量装置

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3727125A (en) * 1970-04-29 1973-04-10 Rhone Poulenc Sa Apparatus for measuring electrostatic properties of materials

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3727125A (en) * 1970-04-29 1973-04-10 Rhone Poulenc Sa Apparatus for measuring electrostatic properties of materials

Cited By (30)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4885543A (en) * 1988-02-16 1989-12-05 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Electrostatic discharge test apparatus
US5604438A (en) * 1995-03-06 1997-02-18 The United States Of America As Represented By The Secretary Of The Navy Controlled spark ignition testing apparatus
WO1996037786A1 (en) * 1995-05-26 1996-11-28 Tr-Tech Int. Oy A measuring system and a method for detecting static electricity and/or change thereof in a measuring object and use thereof
US6031378A (en) * 1995-05-26 2000-02-29 Tr-Tech Int. Oy Measuring system and a method for detecting static electricity and/or change thereof in a measuring object and use thereof
US5699649A (en) * 1996-07-02 1997-12-23 Abrams; Andrew L. Metering and packaging device for dry powders
US5960609A (en) * 1998-06-12 1999-10-05 Microdose Technologies, Inc. Metering and packaging method and device for pharmaceuticals and drugs
US6923979B2 (en) 1999-04-27 2005-08-02 Microdose Technologies, Inc. Method for depositing particles onto a substrate using an alternating electric field
US20100037818A1 (en) * 1999-04-27 2010-02-18 Richard Fotland Method and apparatus for producing uniform small portions of fine powders and articles thereof
US20050158366A1 (en) * 1999-04-27 2005-07-21 Richard Fotland Method and apparatus for producing uniform small portions of fine powders and articles thereof
US7632533B2 (en) 1999-04-27 2009-12-15 Microdose Therapeutx, Inc. Method and apparatus for producing uniform small portions of fine powders and articles thereof
US20080014365A1 (en) * 1999-04-27 2008-01-17 Richard Fotland Method and apparatus for producing uniform small portions of fine powders and articles thereof
US6428809B1 (en) 1999-08-18 2002-08-06 Microdose Technologies, Inc. Metering and packaging of controlled release medication
US6702683B2 (en) 1999-08-18 2004-03-09 Microdose Technologies, Inc. Metering and packaging of controlled release medication
US7404968B2 (en) 1999-08-18 2008-07-29 Microdose Technologies, Inc. Metering and packaging of controlled release medication
US6686743B2 (en) 2000-10-24 2004-02-03 Univation Technologies, Llc Apparatus for measuring the static charge of flowable solids
US20070087048A1 (en) * 2001-05-31 2007-04-19 Abrams Andrew L Oral dosage combination pharmaceutical packaging
US20030155388A1 (en) * 2002-02-05 2003-08-21 Solystic Method of detecting plastics articles, and a detector device
US6888356B2 (en) * 2002-02-05 2005-05-03 Solystic Method of detecting plastics articles, and a detector device
US20090087483A1 (en) * 2007-09-27 2009-04-02 Sison Raymundo A Oral dosage combination pharmaceutical packaging
US9132246B2 (en) 2007-10-09 2015-09-15 Microdose Therapeutx, Inc. Inhalation device
US20090090361A1 (en) * 2007-10-09 2009-04-09 Anand Gumaste Inhalation device
US8439033B2 (en) 2007-10-09 2013-05-14 Microdose Therapeutx, Inc. Inhalation device
US9539400B2 (en) 2007-10-09 2017-01-10 Microdose Therapeutx, Inc. Inhalation device
US20110162642A1 (en) * 2010-01-05 2011-07-07 Akouka Henri M Inhalation device and method
US8991390B2 (en) 2010-01-05 2015-03-31 Microdose Therapeutx, Inc. Inhalation device and method
US9974909B2 (en) 2010-01-05 2018-05-22 Microdose Therapeutx, Inc. Inhalation device and method
US10434267B2 (en) 2010-01-05 2019-10-08 Microdose Therapeutx, Inc. Inhalation device and method
CN103954850A (zh) * 2014-04-22 2014-07-30 重庆大学 一种运动控制机构外置的表面电荷测量系统和测量方法
CN104991129A (zh) * 2015-03-27 2015-10-21 华北电力大学 一种真空绝缘子表面电荷三维测量装置
CN104991129B (zh) * 2015-03-27 2017-11-28 华北电力大学 一种真空绝缘子表面电荷三维测量装置

Also Published As

Publication number Publication date
NL7500371A (nl) 1975-07-23
FR2258632A2 (enrdf_load_stackoverflow) 1975-08-18
DE2502311B2 (de) 1977-01-13
CH592313A5 (enrdf_load_stackoverflow) 1977-10-31
CS182830B4 (en) 1978-05-31
GB1480296A (en) 1977-07-20
FR2258632B2 (enrdf_load_stackoverflow) 1976-10-08
JPS50127670A (enrdf_load_stackoverflow) 1975-10-07
BE824572A (fr) 1975-07-22
IT1031060B (it) 1979-04-30
SE7500576L (enrdf_load_stackoverflow) 1975-07-22
DE2502311A1 (de) 1975-07-24

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